Method and system for reducing autonomous time to fix of a multi-standard GNSS receiver

Abstract

A multi-standard GNSS receiver, handle different global navigation satellite systems (GNSSs), determines with respect to a current time instant, the earliest broadcast timing based on corresponding satellite broadcast cycles for satellites in the different GNSSs. The multi-standard GNSS receiver acquires fresh broadcast ephemeris at the determined earliest broadcast timing to determine its own first position. A search order is determined based on the corresponding satellite broadcast cycles and the current time instant. The multi-standard GNSS receiver may selectively utilize appropriate satellite receivers such as the GPS receiver and the GLONASS receiver to search for satellite signals based on the determined search order. Channels for different GNSSs are scanned to identify transmitting satellites based on the corresponding satellite broadcast cycles for ephemeris downloading. The satellite search is prioritized by comparing the current time instant with the corresponding satellite broadcast cycles.

What is claimed is: 
     
       1. A method for processing signals in a multi-standard global navigation satellite system (GNSS) receiver that is operable to handle a plurality of different global navigation satellite systems (GNSS), the method comprising:
 determining with respect to a current time instant, an earliest time for acquiring fresh broadcast ephemeris from one of the plurality of different GNSSs based on corresponding satellite broadcast cycles for satellites in said plurality of different GNSSs; 
 acquiring said fresh broadcast ephemeris at said determined earliest time; and 
 determining a first position of said multi-standard GNSS receiver based on said acquired fresh broadcast ephemeris. 
 
     
     
       2. The method of  claim 1 , wherein said current time instant is determined from navigation data acquired from one or more of said satellites in said plurality of different GNSSs or from a clock associated with said multi-standard GNSS receiver. 
     
     
       3. The method according to  claim 2 , further comprising:
 determining a search order for said satellites in said plurality of different GNSSs based on said corresponding satellite broadcast cycles and said current time instant. 
 
     
     
       4. The method according to  claim 3 , further comprising:
 searching for signals from said satellites in said plurality of different GNSSs based on said determined search order. 
 
     
     
       5. The method according to  claim 4 , further comprising:
 selectively utilizing another GNSS receive associated with said multi-standard GNSS receiver for said searching. 
 
     
     
       6. The method according to  claim 1 , wherein said corresponding satellite broadcast cycles are associated with channels for said satellites in said plurality of different GNSSs. 
     
     
       7. The method according to  claim 6 , further comprising:
 scanning said channels for said satellites in said plurality of different GNSSs to identify one or more transmitting GNSS satellites based on said corresponding satellite broadcast cycles. 
 
     
     
       8. The method according to  claim 7 , further comprising:
 downloading said fresh broadcast ephemeris from said identified one or more transmitting GNSS satellites; and 
 calculating said first position for said multi-standard GNSS receiver utilizing said downloaded fresh broadcast ephemeris. 
 
     
     
       9. The method according to  claim 1 , further comprising:
 comparing said current time instant with said corresponding satellite broadcast cycles for said satellites in said plurality of different GNSSs. 
 
     
     
       10. The method according to  claim 9 , further comprising:
 prioritizing a manner in which said fresh broadcast ephemeris is acquired from said satellites in said plurality of different GNSSs based on said comparison. 
 
     
     
       11. A system for processing signals, the system comprising:
 one or more circuits for use in a multi-standard global navigation satellite system (GNSS) receiver configured to handle a plurality of different global navigation satellite systems (GNSSs), said one or more circuits being configured to:
 determine with respect to a current time instant, an earliest time for acquiring fresh broadcast ephemeris from one of the plurality of different GNSSs based on corresponding satellite broadcast cycles for satellites in said plurality of different GNSSs; 
 acquire said fresh broadcast ephemeris at said determined earliest time; and 
 determine a first position of said multi-standard GNSS receiver based on said acquired fresh broadcast ephemeris. 
 
 
     
     
       12. The system according to  claim 11 , wherein said current time instant is determined from navigation data acquired from one or more of said satellites in said plurality of different GNSSs or from a clock associated with said multi-standard GNSS receiver. 
     
     
       13. The system according to  claim 12 , wherein said one or more circuits are configured to determine a search order based on said corresponding satellite broadcast cycles and said current time instant. 
     
     
       14. The system according to  claim 13 , wherein said one or more circuits are configured to search for signals from said satellites in said plurality of different GNSSs based on said determined search order. 
     
     
       15. The system according to  claim 14 , wherein said one or more circuits are configured to selectively utilize another GNSS receiver associated with said multi-standard GNSS receiver for said searching. 
     
     
       16. The system according to  claim 11 , wherein said corresponding satellite broadcast cycles are associated with channels for said satellites in said plurality of different GNSSs. 
     
     
       17. The system according to  claim 16 , wherein said one or more circuits are configured to scan said channels for said satellites in said plurality of different GNSSs to identify one or more transmitting GNSS satellites based on said corresponding satellite broadcast cycles. 
     
     
       18. The system according to  claim 17 , wherein said one or more circuits are configured to download said fresh broadcast ephemeris from said identified one or more transmitting GNSS satellites; and to calculate said first position for said multi-standard GNSS receiver utilizing said downloaded fresh broadcast ephemeris. 
     
     
       19. The system according to  claim 11 , wherein said one or more circuits are configured to compare said current time instant with said corresponding satellite broadcast cycles for said satellites in said same GNSS and/or for said satellites in said plurality of different GNSSs. 
     
     
       20. The system according to  claim 19 , wherein said one or more circuits are configured to prioritize a manner in which said fresh broadcast ephemeris is acquired from said satellites in said plurality of different GNSSs based on said comparison.